Holding block for scraper excavating buckets



. Ocf- 22, 1929 o. T. MARTlNsoN Er AL HOLDING BLOCK FOR SCRAPER EXCAVATING BUCKETS Filed Jan. 11, 1928 Patented Oct. 22, 1929 UNITED STATES PATENT OFFICE yOLE T. MARTINSON, OF CHICAGO, AND OSCAR J'. MARTINSON, OF RIVER FOREST, ILLINOIS HOLDING .BLOCK FOR SORAPEB. EXCAVATING BUCKETS Application filed vJanuary 11, 1928. Serial No. 245,914.

This invention relates to holding blocks particularly designed for use with the loading and lifting tackle of scraper excavating bucket. The object of the invention is to provide a holding block, the sheave of which, while freely rotatable in one direction, is provided with load sustaining resistance means opposing movement in an opposite direction and responsive to changes in tension of the cable passing over the sheave. A further purpose of the invention is to provide a holding block of 'this nature in which the sheave or pulley thereof includes relatively movable members arranged to have relative movement only when the cable passing over the sheave is slackened in ord-er to lower the load, and which automatically grip together when the cable is Linder tension for the purpose of sustaining the load with a comparatively slight pulling effort on the cable.

The objects of the invention are accom plished by a construction such as shown in the drawings wherein:

Fig. l is a side view of the improved holding block with part of the casing omitted.

Fig. 2 is'a sectional view taken on the line 2-2 of Fig. 1. g

Fig. 3 is a side view of a scraper bucket and part of its hoisting and loading tackle showing the improved holding block therewith.

Fig. 4 is a sectional view similar to view shown by Fig. 2 but with the sheave modified to receive a chain without slippage.

The construction herein illustrated is intended primarily for use in connection with the loading and lifting tackle for the scraper buckets of drag line excavators. Tn such excavators a bucket is usually suspend-ed, at one side of its center vof gravity, from the end of a boom. Ay loading line or cable draws the bucket in digging operations and also thro-ugh a holding line maintains the bucket more or less in its horizontal position, while the boo-m is swung over to the position where it is desired to dump the bucket. The loading cable also controls the dumping of the bucket through release of tension on the holding line.

Vith the holding blocks as ordinarily constructed iny which the sheaves thereof are freely rotatable in either direction, considerable tension is required on the loading cable to prevent the bucket from unloading until the required time. This tension on the cable necessitates a longer digging stroke of the bucket than is required for filling the bucket and also prevents the utilization of the full length of the boom since the lifting cable is held at a more or less inward angle by the tension on the loading cable.

By means of the present construction, the bucket may be lifted from the soil as soon as filled, and maintained in a load supporting position by comparatively little tension on the loading and holding cables. This slight tension of the holding cable is maintained until the bucket swings to a position substantially below the end of the boom. Therefore the hoisting cable is not held at much of an angle, extending inwardly from the end of the boom, at the time the tension is released on the holding line to permit the bucket to dump.

The improved holding block as shown i Figs. 1 and 2 comprises a casing made of the parts l and 2 bolted together by bolts 3 passing through the ears 4 on the two 'parts of the casing. The casing is spread apart centrally by a steel bushing 5.

Rotatably mounted upon this bushing is ay sheave '6 which is provided with a bronze bushing 7 bearing upon the bushing 5. The sheave 6 carries two sets of spring pressed pawls 8 for coaeting with ratchet wheels 9 and l0 each riveted to one of the parts l and 2 ofthe casing. The teeth of t-he ratchet wheels 9 and 10 extend in the same direction and therefore the sheave is free to rotate to the left, Fig. l, but is prevented from rotating in the right hand direction. The sheave 6 is composed of an inner Wheel shaped part 11, and slidable on the peripheral surface l2 of the part 1l are a series of grooved blocks 13 which altogether compose the grooved element of the sheave for carrying the cable passing thereover. The grooved blocks are normally retained against the inner wheel part 11 of the sheave b the pressure of the holding cable 21, but

efore the cable is reeved through the'device the grooved elements 13 are retained in the assembly by inwardly extending peripheral flanges on the parts 1 and 2 of the casing. Each of the blocks where it bears against the part 11 of the sheave is provided with a facing of brake lining material 14 such as asbestos compositions. Frictional engagement between the blocks 13 and the inner part 11 of the sheaves occurs according to the inward pressure of the blocks 13. This inward pressure is regulated by the load and t-he pulling tension on the cable passing over the sheave. A maximum contact between the cable and the grooved portions of the sheave is provided Vfor by the small grooved wheels 15 journaled in the bottom of the sheave casing and over which the cable passes.

In the operation of the device the sheave may freely rotate to the left, Fig. 1, since in this direction the pawls 8 ride over the teeth of ratchet wheels 9 and 10. The free action of the sheave is not materially affected by the load on the end 16 of the h-olding cable 21 or the amount of pulling effort exerted on-the end 17 of the cable. The operation of the sheave in this direction is not effected by the inward pressure of blocks 13 since these blocks rotate with the inner part 11 of the sheave as a unit. In the opposite direction of movement of the cable the inner part 11 of the sheave should be restrained or is held stationary because of the pawls 8, and the parts 13 of the sheave may slide on the periphery of the wheel part 11. This sliding motion may take place comparatively freely that is under the action of the load on the end 16 of the cable provided the end 17 is not under tension, but if an opposing effort is exerted by maintaining some tension on the end 17 of the cable, the grooved blocks 13 are pressed inwardly so that their inner braking surfaces grip the periphery of the inner part 11. This snubbing action is effective for supporting a considerable load with a comparatively'slight tension of the cable.

The application of the holding block to a scraper bucket is shown in Fig. 3. The hoisting cable by means of which the bucket is suspended from the end of the boom is indicated at 18. Cable 18 is through the bail 19 connected to the bucket, rearwardly of its center of gravity. The improved holding block is attached to the bail 19 at its point of connection with the hoisting cable, and the holding line 21 passing over the holding .block sheave is connected at its end 16 with the upper forward end of the bucket. The opposite end 17 of the holding line is attached to the loading cable 20. With this arrangement the bucket is in the substantially horizontal position shown during the loading operation regardless of the amount of pull on the loading cable. Slight tension on the loading cable 20, and through it on the holding cable 21, serves to prevent the bucket from dumping when the bucket is lifted away from the work. When the bucket arrives at the dumping position tension on the cable 20 is relieved and the mouth end of the bucket swings downwardly around its connection with the bail. The bucket is again returned to the horizontal digging position when tension on the cable 20 is resumed. The digging end of the bucket is swung upwardly around the pivotal connection with the bail by the dump line being drawn through the block by cable 20. At this time the pawls 8 of the sheave idly ride over the ratchet wheels 9 and 10, and the parts 11 and 13 of the sheave rotate as a unit, but after the digging operation when it is desired to prevent the bucket from dumping by maintaining slight tension on the loading cable 20, the pull on the end 17 of the holding line attached to the loadinOr cable and the pull on the end 16 thereo due to the load, causes the grooved blocks 13 to be pressed linwardly against the part 11 of the sheave, thus clutching these parts of the sheave together and preventing rotation of the sheave in a right hand or clock-wise direction, Fig. 1. As soon as the tension on the holding cable 20 is released the bucket swings downward by gravity and releases the load. At this time the tension on the dump line is relieved and the shoes or blocks 13 of the sheave slide around the inner wheel shaped part 11 thereof.

The term sheave as employed in the claims is intended to include modified'forms such as the chain receiving sheave or sprocket wheel shown in Fig. 4.

We claim:

1. A holdingblock of the class described, comprising a casing, a cable receiving element journaled therein, said element having a part relatively rotatable with respect to the remainder of said element but arranged to frictionally grip the same according to the pressure of a cable'thereon.

2. A holding block of the class described, comprising a casing, a cable receiving element journaled therein, said element having a part relatively rotatable with respect to the remainder of said element but arranged to frictionally grip the same according to the pressure of a cable thereon and means for restraining rotation of one of the parts of said element in one direction.

3. A holding block of the class described, comprising a casing, a sheave journaled therein, ratchet means for preventing rotation of said sheave in one direction, said sheave being provided with a grooved peripheral part for receiving a cable, said grooved peripheral part of the sheave being slidable around the inner part of the sheave and arranged to frictionally grip said inner part according to the pressure of a cable on said grooved part of the sheave.

4. A holding block of the class described, comprising a casing, a sheave journaled in said casing, said sheave comprising a wheel portion and a grooved element independently movable with respect to the wheel portion, means for effecting frictional engagement between the grooved element and the wheel portion by the pressure of a cable on said groove'd element, and ratchet means for preventing rotation of the Wheel portion of said sheave in one direction.

5. A holding block of the class described,

'c comprising a casing, a sheave liournaled therein, said sheave being formed of a central wheel and a plurality of shoes slidable on the periphery of said wheel, ratchet means between said casing and said Wheel part of the sheave for preventing rotation of the sheave in one direction, and brake lining between said wheel part of the sheave and said shoes.

Signed at Chicago this 7th day of January,

OLE T. MARTINSON. OSCAR J. MARTINSON. 

